Degree distribution

The degree of a node is the number of connections (links) with other nodes. In the case of directed graphs, each node has two degrees: the out degree and the in degree. In the undirected graph, the relationship is mutual, so we just have a single degree for each node. In the following code snippet we get the source node and target node references from the file links.csv. Then we create a single list to merge the two lists (target and source). Finally, we get a dictionary (dic) of how many times each node appears in the list and we plot the result in a bar chart using matplotlib.

The file links.csv will look as follows:

edgedef>node1 VARCHAR,node2 VARCHAR
23917067,35702006
23917067,629395837
23917067,747343482
23917067,755605075
23917067,1186286815
.  .  .

The complete code snippet looks as follows:

import numpy as np
import matplotlib.pyplot as plt

links = np.genfromtxt("links.csv",
                       dtype=str,
                       delimiter=',',
           ...